I've had a session with Vivienne once, she's even more beautiful in person than the photos. Now, she is ticklish, but I wouldn't say she's a 7/10; she's more a 5. She definitely reacts to being tickled.
It's been a while since I've been on the footspotnyc. Last time I was there they had Emily and Nadia as models. Both were more ticklish than Vivienne. Emily was a pretty Asian girl with really ticklish feet, so I'd say she was an 8/10. And Nadia was a pretty Slavic girl. She's lived in America for a while for still add a little accent. I'd say her feet were more of a 7/10 or 7.5 since she admitted to me that she doesn't like having her feet scrubbed during pedicures, and usually skips that part.
The most ticklish woman I've had a session with was a Korean girl named Daphne form footpadnyc
http://www.footpadnyc.com/daphne. She's was more ticklish than Nadia and Emily. It would even tickle when sucking on her feet, especially her toes.